The leakage current protection device, or ground fault circuit interrupter, is used to detect the ground fault current in electronics, instruments, devices, equipments and electrical systems that are powered by electric grid as well as power supply system. When the ground fault current exceeds specified limit, the circuit protection device will automatically shut down the power supply and so as to protect human being and properties. In actual application, the leakage current protection device or ground fault circuit interrupter may partly or wholly malfunction, and the protection function of the ground fault circuit interrupter thereby malfunction, and the users may not be aware of the situation, thus safety risk may occur.
To solve the problems above, some leakage current protection devices are designed according to IEC 61008-1, IEC 61009-1, GB 6829.1 standards and have a test button, but require a user to manually depress the test button periodically, once a month, to test whether the circuit protection function is working properly. For one aspect, it increases user's workload, and for another, the periodic test must cut down the power supply, and cause inconvenience to user. For the third, if the user does not periodically test the circuit, or the circuit protection device malfunctions during two periodic test periods (such as one month), and safety risk may occur.
To solve the problems above, some ground fault circuit interrupters designed according to UL 943 standard are provided with a self fault detection unit to periodically detect and diagnose the working condition of the ground fault circuit interrupter. However, the circuit and structure of the self fault detection device is too complex, and the manufacturing is difficult, the cost of product is too high, or the practicality is low, which results in the decreased reliability of the original circuit protection function of the circuit protection device due to the additional self detection circuit, and safety risk may occur.